The invention relates to a device in connection with a hand-operated working machine with water flow directed to the working tool, comprising a first control which is a control for a drive motor for the tool, and a second control which is a control for the water supply to the tool.
Hand-operated working machines of the above type are used for many operating purposes mainly in the building industry, especially in connection with reconstruction and enlargement jobs. Cutting, sawing and drilling work are common for cutting openings for doors and windows, for cutting ventilation ducts, foundations and many other things. In the rescue service there is also used machines of this type, for example in order to saw car roofs, house roofs etc. Concretexe2x80x94even with reinforcing ironsxe2x80x94bricks, sheet steel, etc are common to work on. Cooling of the tool by water flow is therefor a standard procedure. U.S. Pat. No. 5,038,474 discloses a device in connection with a cutting machine (circular saw) with an annular saw blade with a double walled disk on the inside of the annular saw blade with outlet openings near the periphery of the disk and with an inlet opening for the cooling water near the drive machinery for the rotation of the blade. U.S. Pat. No. 5,038,474 also shows other main components of the machine, comprising a machine body with a front handle bow and a rear handle. It is also known for this type of machines to arrange, for security reasons, the control for the drive motor, no matter if it is a hydraulic motor, a combustion motor or an electric motor, so that the motor can not be rushed by mistake, if, for example, the operator would stumble or fall. More precisely, there is a latch which in connection with machines driven by a combustion motor would be referred to as a gas latch, but which more generally can be called an accelerator latch, a term which will be used in this text. This accelerator latch first must be pressed by the operator in order to make it possible at all to affect the drive motor control and thereafter remain activated in its functioning position as long as the machine is being operated. As soon as the motor is allowed to run idle, the accelerator latch returns to its original position and must be activated anew before the drive motor control can be affected again.
It is also known to arrange some kind of valve for the water supply, so that the water can be let on and shut off and also be adjusted for different flows. This valve conventionally has been placed in connection with the connection of the water conduit to the machine body. This arrangement makes it impossible, or substantially more difficult, to control the water supply. Either, the water has had to be let on before the cutting work or corresponding is started, which is not convenient, or the work has had to be interrupted in order to start or adjust the water flow, which is not convenient either from a working efficiency or security point of view.
The object of the invention is to address the above problem complex. The main distinguishing feature of the invention is that a water control valve in a water supply conduit can be adjusted to adopt chosen opening positions, that the valve is arranged to be constantly kept open in any chosen opening position when the motor runs the tool under influence of the drive motor control, and that the chosen opening positions are adjustable, i.e. that the through opening of the valve can be increased or decreased by means of said control for the water supply. The water control valve is preferably arranged to be forcedly kept open in a chosen opening position when the motor runs the tool. This can be accomplished by means of a third control, which together with said first and second controls is arranged in connection with a rear handle on the machine, preferably so that all three controls can be reached and manoeuvred by the operator by that hand with which he at the same time is holding a rear handle on the machine. The third control is preferably an accelerator latch, see above, for the drive motor, i.e. a means which must have been activated by the machine operator in order that the first control, the drive motor control, shall be possible to be activated. The alternative that the third control has not any other function than to keep the valve open, i.e. is arranged only for that purpose, is however also plausible, but that is generally to be considered a less beneficial alternative than to give the accelerator latch a two-purpose function.
The device of the invention can be designed in many different ways within the scope of the invention. A beneficial model which will be described in greater detail in the following is based on a lever mechanism and is characterised in that the water control valve is arranged to be influenced by a first lever arm -which is an integrated part of or is in its turn possible to affect by said third control. A second lever arm for adjustment of the water control valve is included in the same lever mechanism. More particularly, this can be carried out by the second lever arm being arranged to affect the first lever arm for adjustment of the water control valve in connection with the adjustment of the water supply control. The water supply control in this case may comprise e.g. a cam disc which is rotatable about a shaft in order thereby to be able to affect the second lever arm.
Further characteristics and aspects of the invention appear from a number of dependent claims and from the following description of a preferred embodiment. The embodiment relates to the device according to the invention in use on a cutting machine with annular saw blade. It should however be understood that the principles of the invention can be used also on other machines of the kind mentioned in the preamble, as e.g. cutting discs with traditional centre drive of the cutting blade, cutting machines with chain saw and so on. Different types of drive machinery are also conceivable, such as hydraulic motors, combustion motors and even electrical motors.